The pipe is in particular a flexible pipe of the unbonded type designed to transfer hydrocarbons through an expanse of water, such as an ocean, sea, lake or river.
Such a flexible pipe is for example made according to normative documents API 17J (Specification for Unbonded Flexible Pipe) and API RP 17B (Recommended Practice for Flexible Pipe) established by the American Petroleum Institute.
The pipe is generally formed by a set of concentric and superimposed layers. It is considered “unbonded” within the meaning of the present invention when at least one of the layers of the pipe is able to move longitudinally relative to the adjacent layers when the pipe is bent. In particular, an unbonded pipe is a pipe with no bonding materials connecting the layers forming the pipe.
The pipe is generally positioned through an expanse of water, between a bottom assembly, designed to collect the fluid recovered in the bottom of the expanse of water, and a floating surface assembly designed to connect and distribute the fluid. The surface assembly may be a semisubmersible platform, an FPSO or another floating assembly.
In a known manner, such a pipe includes a tubular inner structure comprising at least one pressure sheath. The pipe includes plies of tensile armor positioned around the inner tubular structure.
In some cases, for the exploitation of fluids in deep water, the flexible pipe has a length exceeding 800 m. The ends of the pipe have end-pieces for connecting to the bottom assembly and the surface assembly.
These pipes undergo very high axial tensile forces, in particular when the expanse of water in which the pipe is positioned is very deep.
In that case, the upper end-piece connecting the pipe to the surface assembly must react a very significant axial tension, which may reach several hundreds of tons. These forces are transmitted to the end-piece by means of plies of tensile armor extending along the pipe.
The assembly of the end-pieces of the pipe, in particular, the end of the plies of tensile armor in the end-piece, is a critical step to preserve the integrity of the pipe during its use.
To that end, during the assembly of the end-piece, the end segments of the armor plies are unstuck from the inner structure of the pipe and are folded rearwards to allow the insertion of a crimping assembly of the inner sheath of the pipe.
The end vault of the end-piece is next inserted at the end of the inner structure, and the end segments of the armor plies are folded toward the axis of the pipe against the vault.
Then, an outer cover of the end-piece is fastened on the vault, around the end segments of the armor plies and a material capable of solidifying is inserted into the intermediate chamber situated between the cover and the vault, so as to embed the end segments.
The separation of the end segments of the armor plies away from the inner structure must be done carefully to avoid damaging or mechanically biasing the end segments of the armor threads, so as to preserve their longevity over time.
To that end, WO 03/004921 describes an assembly method in which a three-part metal locking collar is engaged around armor plies behind the desired separation point.
Next, an annular guide made from a material making it possible to preserve the surface of the armor threads, for example nylon, is positioned on the locking collar.
The end segments of the outer ply are next folded rearwards around the annular guide, the end segments of the inner ply remaining pressed against the inner structure.
The nylon annular guide has a curved front surface that limits the curvature of the armors when they are folded rearwards.
Next, the anti-wear strip positioned between the inner ply and the outer ply is cut as close as possible to the separation point of the end segments of the outer ply, near the locking collar. The end segments of the inner ply are next turned over directly on the end segments of the outer ply substantially following the same curve radius.
The front crimping assembly and the vault are next placed, and the end segments are folded forward against the vault.
Such a method may be further improved. Indeed, the anti-wear strip positioned between the inner ply and the outer ply is cut as close as possible to the separation point of the outer ply. As a result, when the end segments of the two plies are folded toward the vault of the end-piece, the end segments of the outer ply may rub against those of the inner ply at the separation point, in the zone where the armor threads are hardened and where the mechanical strength is lower.
In some cases, this may lead to weakening of the mechanical properties of the pipe.